Multiple variable rate audio message playback

ABSTRACT

Method and apparatus for recording and playing back a plurality of digitally encoded audio messages along with associated video data. The messages are combined along with a plurality of corresponding audio message initial data address signals and recorded on a recording medium with the video data. In playback, the address and audio data signals are retrieved from the recording medium and stored. The address signals are utilized to access selectable messages for decoding and playback with selected video data. Codes can be included to control the decoding rate in accordance with the sample rate of the audio message data.

CROSS-REFERENCE TO RELATED APPLICATlON

This application is a continuation of application Ser. No. 342,291,filed Jan. 25, 1982 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to audio frequency information encodingand decoding, and more particularly relates to audio message encodingand recording on a recording medium for later retrieval, decoding andplayback with related video information which is recorded with the audioinformation on the same recording medium.

2. Brief Description of the Prior Art

"Stop-motion" is a technique in the playback of recorded videoinformation whereby a single frame of recorded video signals is playedrepeatedly to provide a continuous video picture of the visualinformation contained in the single frame being played. Stop-motiontechniques are known and are in widespread use in TV broadcasting, themost well-known example being in the area of televised sportsbroadcasts. In such broadcasting applications, the recording mediumgenerally used to create the stop-motion effect is the video tape.

A development which has made the stop-motion capability attractive forapplications other than broadcasting is the optical disc. An opticaldisc is a flat disc approximately the size of an LP phonograph recordwhich is made of clear plastic and is capable of having informationrecorded on an imbedded surface in the interior of the disc in form ofspiralling or circular tracks of optically readable indicia. Opticaldiscs are read by imaging a beam of light to a tiny spot on a track,rotating the disc and thus causing the spot of light to scan linearlyalong the track, and detecting with a photodetector the amount of lightwhich emerges from the track in a selected direction. Information isstored in the disc in the pattern in which the indicia are provided onthe track. As the disc is scanned by the spot of light, the amount oflight which is detected varies in accordance with the alternate presenceand absence of the indicia, and the information is recovered bydetecting the electrical signal variations of the photodetector outputproduced by the particular pattern of indicia on the track.

The most widely-used format for the recording and playback of videoinformation on an optical disc involves frequency modulating a videocarrier and one or more audio subcarriers, combining thefrequency-modulated carrier and subcarriers, and then varying thespatial frequency and relative length of the indicia, as compared withthe areas between them, in accordance with the frequency-modulatedcarrier and subcarrier signals.

It is possible to record video information on an optical disc such thatareas of the track corresponding to vertical sync intervals are alignedradially on the disc. Such discs are called Constant Angular Velocity("CAV") discs because in the recording and playback of videoinformation, such discs are rotated at a constant angular velocity.

CAV discs provide several useful features which result from the factthat the vertical sync intervals in every track on the disc line up inthe same radial direction. This arrangement makes it possible whilereading the disc to jump from track to track with relative ease whilemaintaining the synchronization of the horizontal and vertical syncoscillator circuits of the television or monitor being driven by thedisc player output. This is made possible because, as the spot of lightarrives at a new track after being jumped from a previous track, thesynchronization of the video information recorded in that track isidentical to the synchronization of the video information in the trackfrom which the spot was just removed. Thus, after making such a jumpthere is no need to reestablish lost synchronization, and instead theplaying of the video information can proceed smoothly and withoutinterruption.

This capacity to jump smoothly among frames of video information hasmade the optical disc a highly suitable recording medium for videoinformation intended for play in the stop-motion mode. For example, anentire optical disc can be recorded exclusively with stop-motion videoinformation. In such a case each video frame recorded on the disccontains a different picture, and the disc can be read frame by frame,and thus picture by picture, as one would read a book, by playing eachframe in stop-motion mode and accesing individual frames as desired.Considering that over 50,000 frames of video can be stored on a singleside of a CAV disc, the utility of such a format is obviously very wide.For example, an entire department store catalog or an entire 100,000picture educational program can be placed on a single optical disc.

Stop-motion features of the optical disc become even more attractivewhen combined with the capability of audio playback during thestop-motion playing of the video information.

Techniques have been devised for the recording of audio information forplayback with a frame of stopmotion video. According to one technique,set forth in co-pending U.S. patent application Ser. No. 202,840, filedon Oct. 31, 1980, issued on July 31, 1984 as U.S. Pat. No. 4,463,389 inthe name of Scott M. Golding, incorporated herin by reference, andcommonly assigned to the assignee of the present invention "stop-motionaudio" to be played back with an accompaying stop-motion frame of videois encoded in a digitized form, for example by adaptive deltamodulation, and recorded on one of two available audio channels on thedisc. During playback, prior to the playback of the associatedstop-motion video frame, the digitally encoded stop-motion audioinformation is read from the audio channel and stored in a storagedevice such as a RAM. When the stop-motion frame is played, thedigitized audio information is read out of the storage device, decodedand played along the stop-motion video.

One of the limitations of this technique is that the bit rate of thedigitized audio data as it is read from the disc must be kept within thebandwidth limitations of the audio channel on which it is recorded. Atypical value which has been used with this technique is a read bit rateof twelve kilohertz. When employing adaptive delta modulation, samplingbit rates in the encoding process are typically sixteen kilohertz orgreater to provide desired intelligibility. Thus, according to thistechnique, the disc must be played in the normal mode of operation for aperiod of time just slightly longer than the duration of the stop-motionmessage in order to read the encoded stop-motion message in memory. Thetechnique is therefore not useful for recording programs having a largenumber of closely-spaced stop-motion frames. It does, however, provide arelatively low-cost way of recording and playing back stop-motion audioinformation where stop-motion frames are provided at more widely-spacedintervals throughout the program.

A second technique, described in co-pending U.S. patent application Ser.No. 066,620, filed on Aug. 15, 1979 now abandoned in favor of Ser. No.161,231, filed June 18, 1980, in the name of Wayne R. Dakin one of theinventors of the present invention and commonly assigned to the assigneeof the present invention, also involves the encoding of stop-motionaudio information, for example by adaptive delta modulation. However,the digitally encoded stop-motion audio information is recorded in theplace of video information on one or more successive frames. Thestop-motion audio information message is encoded at a desired samplingrate, such as sixteen kilohertz and then time compressed to a bit rateof 7.2 megahertz and encoded such that the bandwidth is within thecapabilities of the video electronic circuitry. The encoded data is thenprovided in the place of the video information in the horizontal linesof the video frames. The large time compression of the digitized audioinformation permits the storage of stop-motion audio messages of aduration of up to eleven seconds in the video data portion of a singleframe of video. The electronic circuitry required to implement thissecond technique is more costly than that associated with the firsttechnique described above, but the later techniques permits considerablymore stop-motion audio message information to be stored on an opticaldisc. Thus, an optical disc can be formatted in an alternating sequenceof stop-motion video frames and stop-motion audio frames to provide eachvideo frame with a stop-motion audio message of up to eleven seconds induration. This "video encoding" technique, therefore, represents anenormous improvement in the efficiency of storing digitally encodedstop-motion audio messages on an optical disc.

The video encoding technique has certain limitations, however. Programdemands for stop-motion message duration vary considerably. Videoprogrammers frequently require only two or three seconds for aparticular stop-motion frame, but occasionally require a stop motionaudio message of up to twenty seconds or more. This presents problems inselecting a format for the stop-motion audio information. For reasons ofeconomy it is desirable to have a standard format for stop-motion audioinformation recording and playback so that video optical disc playershaving stop-motion capability do not have to be redesigned for every newprogram. A reasonable compromise standard format for stop-motion audioencoding is two successive frames of video field devoted to a singlestop-motion audio message sampled at a rate of sixteen kilohertz. Such aformat enables the storage and playback of stop-motion audio messages ofup to twenty-two seconds in duration at a reasonable level ofintelligibility. This permits the storage and playback of all but themost lengthy stop-motion audio messages in most program applications.However, most stop-motion audio messages are considerably less inlength, some lasting for only two or three seconds, as was mentionedpreviously. For such stop-motion messages an enormous amount of storagecapability is wasted. Even if only a single frame were to be devoted toa single stop-motion audio message, the eleven seconds afforded at asixteen kilohertz bit rate would still be excessive for many stop-motionaudio messages, and longer messages could not be recorded in such aformat.

In addition, while a sixteen kilohertz bit rate in connection withadaptive delta modulation is one which provides a reasonable compromisebetween intelligibility and data packing density requirements, audiomessage information played back at a sixteen kilohertz sampling ratedoes not provide full fidelity. Frequently it is desirable to providesuch increased intelligibility, but prior art techniques do not providethe flexibility to do so.

Accordingly, it will be appreciated that there is a need for a videorecording and playback system having stop-motion audio recording andplayback capabilities which overcome the above-noted limitations. Inparticular, there is a need for such a system which provides moreflexibility in the provision of stop-motion audio messages on arecording medium while preserving standardization to permit theeconomical manufacture of the associated apparatus.

The present invention fulfills these needs.

SUMMARY OF THE INVENTION

The present invention resides in a method and apparatus for therecording and playback of audio messages along with selected video data.According to one aspect of the present invention, a method is providedfor recording a sequential series of digitally encoded audio datasignals onto a recording medium along with associated video data suchthat predetermined message portions of the audio data can be selectablyrecovered for separate decoding and playback with selectable portions ofthe video data.

On the recording medium the record audio messages, together withassociated recorded address data signals, form a block of compositedata. The block of composite data is arranged in a prescribed manner soas to aid in recovery and playback of a selected audio message withconvenience and high efficiency. This is accomplished in the followingmanner. Each audio message is preceded by an identification address, andthe combination of the identification address and associated audiomessage is referred to herein as an audio message unit. Thus, there isrecorded on the medium a continuous stream of digitized audio datadefining up to eight separate audio message units, in a preferredembodiment.

At the head of each block of composite data, before the first messageunit, is a header containing a number of message pointers equalling thenumber of message units in the block. Each message pointer contains anaddress that is the same as the identification address of itscorresponding message unit in the series of message units.

The block of composite data is recorded along with the visual-video dataonto the recording medium, such that the composite data is recoverablefrom the recording medium for storage at predetermined addressablestorage locations, and such that the addresses of the predeterminedstorage locations are correlated with the identification addresses ofthe stored message units. That is, when the block of composite data isstored in the memory device of the player, the message units are storedat locations determined by the respective identification address of eachmessage unit. According to the invention, when a particular audiomessage is to be outputted, a memory pointer is selected by the user;the selected memory pointer, containing the address of a correspondingmessage unit stored in the memory, enables the message unit to beretrieved from the memory location having the same address; and theaudio message is then separated from the identification address to bedecoded and outputted through the audio channel of the player whileviewing selected viewable-video data.

As will be explained in more detail later in an alternate embodiment ofthe invention, the contents of a pointer includes more digitalinformation than just the identification address of the correspondingmessage unit. The common portion of the pointer address, i.e. thatportion which uniquely matches that of the identification address of thecorresponding audio message unit, is used to retrieve the selectedmessage unit from the memory. That portion of the pointer address notcommon with the identification address is used to establish outputsampling rate. The pointer is accessed from its storage position inmemory; the address contained in the pointer is then used to access thecorresponding message unit from its storage location; and the audiomesage portion of the message unit is then decoded and outputtedsimultaneously with the outputting of selected visual video data fromthe player.

According to another aspect of the present invention, a method isprovided for recording a sequential series of digital audio datasignals, encoded at a predetermined variable sampling rate onto arecording medium along with associated video data signals, such that theaudio data signals are recoverable for decoding at the predeterminedvariable sampling rate and for playback with the video data. Apredetermined digital signal representative of the predeterminedsampling rate is generated and combined with the audio data signals in apredetermined relative relationship therewith to form a composite groupof digital signals. The composite group of digital signals is recordedalong with the video data signals such that the predetermined digitalsignal is recoverable from the group of digital signals fo setting thesampling rate for decoding the encoded audio to the predeterminedvariable sampling rate. The composite group of audio data signals isrecovered from the storage medium during playback and then stored in amemory. The predetermined digital signal is recovered and theinformation therein relating to the predetermined sampling rate is usedto set the bit rate of a decoder. The audio data signals are decoded atthe predetermined sampling rate and the recovered audio is played with apredetermined portion of the video data.

It will be appreciated from the foregoing that the present inventionrepresents a significant advance in the field of stop-motion audiorecording and playback systems, as well as in audio data storage systemsin general. In particular, the invention provides an effective techniquefor the storage of stop-motion audio messages for later playback withassociated stop-motion video data such that considerably expandedflexibility in quality and duration of such messages is provided ascompared with prior art techniques. Other aspects and advantages ofpresent invention will become apparent from the following more detaileddescription, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a stop-motion audio decoder constructedaccording to the principles of the present invention.

FIG. 2 is a diagram of the format of a block of encoded audio data whichis used in connection with the present invention.

FIG. 3, consisting of 3A and 3B, is a diagram of the data structure of aRAM loaded with data in accordance with the principles of the presentinvention.

FIGS. 4A and 4B are schematic diagrams of the control circuit shown inFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a block diagram of a stop-motion audio data recovery anddemodulation apparatus constructed according to the principles of thepresent invention. A standard video disc player apparatus 10 reads anoptical disc (not shown) and provides as outputs a video signal line 12carrying recovered video information, and audio signal line 14 carryingrecovered audio information from Audio Channel 2, which is one of thetwo audio channels provided on the videodisc and a Command signal line16. The video signals on line 12 are applied to a video data recoverycircuit 20.

The video data recovery circuit 20 processes the video signal input online 20 and provides as outputs four parallel lines of digitally encodedaudio data at logic level, recovered from two successive frames ofvideo. The recovery circuit 20 also provides a clock signal as an outputon line 24, which is the clock rate of the encoded data output on line22. The clock pluses on line 24 are applied to a conventional four-bitparallel to eight-bit parallel converter 26, which converts the four-bitparallel data input on line 22 into eight-bit parallel data ("VideoCoded Data"), which is applied to a control circuit 28 on line 30. Theclock pulses on line 24 are also applied to a conventionaldivided-by-two circuit 32, the output of which ("Video Clock Data") isapplied to the control circuit 28 on line 34. The details of thecircuitry in the video data recovery circuit 20 are set forth incopending U.S. patent application Ser. No. 218,584, filed on Dec. 19,1980 in the names of Jordan Isailovic and Wayne Ray Dakin and commonlyassigned to the assignee of the present invention.

The audio signal on line 14 is applied to an audio data recovery circuit36, which recovers digitally encoded audio data as a serial bit streamat logic level from the audio signal on line 14. The encoded audio datais applied as an output on line 38 to a conventional serial to eight-bitparallel converter 40, which converts the serial stream of encoded audiodata on line 38 into eight-bit parallel data ("Audio Coded Data"), whichis applied to the control circuit 28 on line 43. The audio data recoverycircuit 36 also provides as an output on line 44 a clock signal at therate of recovered Audio Coded Data, which is applied to theserial-to-parallel converter 40. The clock signal on line 44 is appliedto a conventional divide-by-eight circuit 46 which divides the clockpulse stream by eight and applies the resultant output ("Audio ClockData") to the control circuit 28 on line 48. The details of theprinciples of construction and operation of the audio data recoverycircuit 36 are provided in the aforementioned copending U.S. patentapplication Ser. No. 202,840.

The control circuit 28 communicates in conventional manner with a 48KRAM 50 by way of a WRITE CLOCK line 52, WRITE DATA line 54, RAM ADDRESSline 56, READ CLOCK line 58 and READ DATA line 60. The control circuit28 applies data retrieved from the RAM 50 on a line 62 to an adaptivedelta demodulator 64. Clock pulses are also applied on line 66 to theadaptive delta demodulator for decoding the retrieved data on line 62 atthe appropriate rate. The recovered adaptive delta demodulated audio isapplied on an output line 68 for subsequent filtering and amplificationfor playing with associated video.

The Video Coded Data on line 30 and the Audio Coded Data on line 42 areclocked at different rates. The Video Coded Data on line 30 is clockedat a rate of approximately 900 kHz, while the Audio Coded Data on line42 is clocked at a rate of approximately 1,500 Hz. Both the Video CodedData and Audio Coded Data, however, have the same format.

FIG. 2 is a block diagram which shows the format of the Audio Coded Dataand Video Coded Data. At the beginning of a block of either Video CodedData or Audio Coded Data, a series of sixteen-bit message unit pointers70-84 are provided, which together comprise a "Header" 88 of data.Following the Header 88, continuous stream of digitized Audio Data 86 isprovided. The Audio Data 86 is comprised of up to eight separate audiomessage units appearing serially to make up the entire segment of AudioData 86. The message unit pointers 70-84 each comprise a sixteen-bitbyte, which is a digital number corresponding to the position of thefirst byte of data in an associated audio message unit in the segment ofAudio Data 86, and to the sampling rate of the data in the unit. Becausethe block of Audio Coded Data or Video Coded Data is loaded seriallyinto the 8-bit storage locations in the RAM 50, starting with address0000, the message pointers are selected to include the RAM address ofthe first 8 bits of data in the associated message unit when the data isloaded in the RAM 50 in this way.

In operation, a block of Video Coded Data or of Audio Coded Data is readinto the RAM 50 by the control circuit 28 in response to a commandsignal on Command line 16. Subsequently, in response to a furthercommand signal on line 16, a selected message pointer is retrieved andprocessed to obtain the address of the first 8 bits of the associatedmessage unit and the sampling rate of that unit of data. Subsequently,the portion of the Audio Data 86 corresponding to the entire audiomessage unit selected is retrieved from the RAM 50 and clocked out at anappropriate rate to the adaptive delta demodulator 64 where the audiomessage unit data is demodulated and output on line 68 for furtherprocessing.

FIG. 3A depicts the structure of data stored in the RAM 50 memory afterit is loaded with a block of either Audio Coded Data or Video CodedData. In the diagram, the RAM 50 storage location designated "0000" isat the leftmost portion of the diagram, and storage locations havingsequentially increasing addresses proceed from the left to the right.All addresses are expressed in Hex notation. Thus, the addresses of theavailable storage in the 48K RAM 50 proceed from 0000 to BFFF.

The data is stored in the RAM 50, as depicted in FIG. 3A, such that theHeader 88 occupies a portion of RAM 50 memory having address 0000 to000F. A portion of audio data corresponding to a first message unit"Message Unit 1", occupies an area of storage from address 0010 through1F3F. Message Unit 2 occupies storage locations having addresses 1F40through 2AEF, and so on. In all, five mesage units, MUI-MU5, are loadedin RAM 50.

FIG. 3B is an expanded diagram of the portion of RAM 50 memorycontaining the Header 88 previously discussed. The data 88 occupies 16eight-bit portions of memory having associated addresses 90, indicatedbelow each vertical column representing each eight-bit storage locationof RAM 50 memory. Data is arranged in the figure in each memory locationsuch that the least significant bit appears at the top of the column,and the most significant bit appears at the bottom.

As was mentioned previously in connection with FIG. 2, each message unitpointer 70-84 comprises a sixteen-bit byte. Thus, each message unitpointer occupies 2 eight-bit storage locations in the RAM 50. Message 1pointer occupies memory at addresses 0000 and 0001, Message 2 pointer 72occupies storage locations having addresses 0002 and 0003, and so on.RAM 50 memory having address 000A through 000F are not needed in thisexample to store further message pointers and are consequently loadedwith zeros.

It will be noted that the Hex notation addresses of the first eight bitsof data for each of the five message units 1-5 are, from FIG. 3A, 0010,1F40, 2AF0, 32D0, and 6590, respectively. However, the message unitpointer 1-5 stored in the Header 88 portion of the RAM 50 are, from FIG.3B, 0018, 1F45, 2AF0, 32DB and 659F, respectively. Thus, it will beappreciated that while the three most significant Hex digits of themessage unit pointers correspond to the three most significant Hexdigits of message unit addresses, the least significant digit may notcorrespond. In fact, all of the least significant digits of the messageunit addresses are 0, and the least significant digit of the messageunit pointer is used to designate the sampling rate for the Audio Datain the message unit of the associated pointer. The sampling rate code isdescribed in detail below.

FIG. 4 is a circuit diagram of the control circuit 28 of FIG. 1. TheVideo Clock line 34 is connected to the Low input of a first multiplexer92, and the Audio Clock line 48 is connected to the High input ofmultiplexer 92. The Select input of multiplexer 92 is connected to theoutput of a comparator 94. The output of multiplexer 92 is connected toone input of an AND gate 98, the output of which is connected to line52. The eight-bit command line 16 is connected to a first input ofcomparator 94 as well as to first inputs of further comparators 100 and102 and to the Select inputs of a second multiplexer 104 and a thirdmultiplexer 106. A switch 108 set to the Hex notation number 56 ("Hex56") is connected to the second input of comparator 100. A switch 110set to Hex 41 is connected to the second input of comparator 94, and aswitch 112 set to Hex 3 is connected to the second input of comparator102. The output of comparator 100 is connected to a first input of an ORgate 114, the output of which is connected to the second input of ANDgate 98 and to the control input of a tri-state buffer 116. The outputof comparator 94 is connected to the Select input of the multiplexer 92,as was mentioned previously, and also to the second input of OR gate 114as well as to the Select input of a second multiplexer 118.

The Video Coded Data line 30 is connected to the Low input ofmultiplexer 118, while the Audio Coded Data line 42 is connected to theHigh input of multiplexer 118. The output of multiplexer 118 isconnected to the input of the tri-state buffer 116. The output of thetri-state buffer 116 is connected to line 54. The output of AND gate 98is also connected to the Clock input of a sixteen bit counter 120. Theoutput of the counter 120 is connected to the Low input of a fourthmultiplexer 122, the output of which is connected to the Low input of afifth multiplexer 124. The output of multiplexer 124 is connected toline 56.

The output of comparator 102 is connected to the Load input of a furthersixteen bit counter 126, the rising edge input of a one shot 128 and tothe Select input of multiplexer 122. The output of counter 126 isconnected to the High input of multiplexer 122. The output ofmultiplexer 104 is connected to the input of counter 126, while theoutput of multiplexer 106 is connected to the input of a furthercomparator 130.

The output of comparator 130 is connected to the first input of an ORgate 131, the output of which is connected to the rising edge input of aone shot 132. The second input of OR gate 131 is connected to anexternal line 133. The Q output of one shot 132 comprises an initializepluse and is connected to the CLEAR input of comparator 130, to the SETinput of a first flip-flop 134, to the CLEAR input of counter 120, andto the RESET input of a second flip-flop 136. The output of one shot 132is also connected to the CLEAR Inputs of comparators 94, 100 and 102, aswell as to the CLEAR Input of a further sixteen-bit counter 138 and tothe RESET input of a third flip-flop 140.

The Q output of flip-flop 134 is connected to the HOLD Input of aVariable Rate Clock Generator 142. The output of the Clock Generator 142is connected to the input of a divide-by-eight device 144, to the CLOCKinput of a parallel-to-serial converter 146, and to a first input of afurther AND gate 148. The output of the divide-by-eight device 144 isconnected to the LOAD input of the parallel-to-serial converter 146, tothe SET input of the third flip-flop 140, to one input of a further ANDgate 150, and the CLOCK input of counter 138. The Q output of flip-flop140 is connected to the second input of AND gate 148, the output ofwhich is connected to line 66. The output of the parallel-to-serialconverter 146 is connected to line 62.

The output of counter 138 is connected to the second input of comparator130 and to the HIGH input of multiplexer 124. The output of multiplexer124 is connected to line 56.

The Q output of one shot 128 is connected to the LOAD input of aregister 152, to a first input of a further AND gate 154, and to therising edge input of a second one shot 156. The Q output of one shot 156is connected to the second input of AND gate 154, the output of which isconnected to the second input of AND gate 150. The output of AND gate150 is connected to line 58. The Q output of one shot 156 is alsoconnected to the input of a delay line 158, to the LOAD input of afurther register 160, and to the CLOCK input of counter 126.

The output of the delay device 158 is connected to the SET input offlip-flop 136, to the LOAD input of counter 138, and to the RESET Inputof flip-flop 134. The Q output of the second flip-flop 136 is connectedto the SELECT input of multiplexer 124.

Line 60 is connected to the input of the parallel-to-serial converter146 and also to the inputs of registers 152 and 160. The eight-bitparallel line output of register 152 and the eight-bit parallel lineoutput of register 160 are combined to form a single sixteen-bitparallel line 161, the four least significant bits of which areconnected to the SELECT input of the clock generator 142 and the twelvemost significant bits of which are connected to the input of counter138.

Multiplexer 104 and multiplexer 106 are each 8:1 multiplexers whichselect among eight inputs according to a binary number present at theSELECT inputs thereof. The first input of multiplexer 104 is connectedto a switch 162 set to the RAM 50 address of the first eight bits of thefirst message unit pointer. The second input of multiplexer 104 isconnected to a switch 164 set to the RAM 50 address of the first eightbits of the second message unit pointer, and so on, up to switch 166 setto the RAM 50 address for the first eight bits of the eighth messageunit pointer and connected to the eighth input of mulitplexer 104.

The first input of multiplexer 106 is connected to a switch 168 set tothe RAM 50 address of the first eight bits of the second message unitpointer. The second input of mulitplexer 106 is connected to a switch170 set to the RAM 50 address for the first eight bits of the thirdmessage unit pointer 170, and so on, up to the seventh input of themultiplexer 106. The eight input of the multiplexer 106 is connected toa switch 172 set to the RAM 50 address corresponding to the end of theRAM 50 storage area used to store the stop motion audio data.

Before proceeding with a description of the operation of the circuitshown in FIG. 4, the format of the sampling rate code memntionedpreviously should be understood. The following table, Table 1, setsforth the sampling rate code:

                  TABLE 1                                                         ______________________________________                                        Sampling Rate Code                                                            Hex Bit Value Sampling Rate (KHz)                                             ______________________________________                                        0             13                                                              1             14                                                              2             15                                                              3             16                                                              4             17                                                              5             18                                                              6             19                                                              7             20                                                              8             21                                                              9             22                                                              A             23                                                              B             24                                                              C             25                                                              D             26                                                              E             27                                                              F             28                                                              ______________________________________                                    

It will be recalled that Message Unit Pointers 1-5 comprise thefollowing Hex numbers: 0018, 1F45, 2AF0, 32DB, and 659F. The leastsignificant digit in each of the pointers comprises the sampling ratecode for the associated Message Unit. Thus, referring to Table 1, thesampling rate for the first Message Unit is 21 KHz, that for the secondMessage Unit, 18 KHz, that for message Unit 3, 13 KHz, and so on.

The format of the command codes transmitted on command line 16 shouldalso be understood. The following table, Table 2, sets forth the commandcode:

                  TABLE 2                                                         ______________________________________                                        Command Code                                                                  ______________________________________                                        56             Get Video Coded Data                                           41             Get Audio Coded Data                                           31             Play Message Unit 1                                            32             Play Message Unit 2                                            33             Play Message Unit 3                                            34             Play Message Unit 4                                            35             Play Message Unit 5                                            36             Play Message Unit 6                                            37             Play Message Unit 7                                            38             Play Message Unit 8                                            ______________________________________                                    

A Get Video Coded Data command signal (Hex 56) activates the controlcircuit 28 to receive Video Coded Data and read it into the RAM 50. AGet Audio Coded Data command signal (Hex 41) activates the controlcircuit 28 to receive Audio Coded Data and read it into the RAM 50. ThePlay Message 1-8 command signals (Hex 31-38) activate the circuit toretrieve Message Units 1-8, respectively, from the RAM and clock themout at the appropriate rate to the adaptive delta demodulator.

The circuit shown in FIG. 4 operates in the following manner.

Initially, on power up of the system a logic level "1" pulse isgenerated in a conventional manner and applied to line 133. This clearsthe comparators in the circuit and sets the circuit to a readyconditions to receive a block of data.

If a block of Video Coded Data is to be received from the player 10(FIG. 1) a Get Video Coded Data command code which, from table 2 is theHex number 56, is applied to the 8 bit command data line 16. The GetVideo Coded Data code is generated just prior to the reading of theblock of Video Coded Data from the disc. Since it will always be knownwhere on a given disc a block of encoded Video Coded Data is recorded,it is a simple matter to control the timing of the appearance of thecommand signal on line 16. For example, if a block of Video Coded Datais recorded in the video portion of the 10,000th and 10,001st frames,the conventional circuitry within the video disc player 10 may beutilized to generate a signal at the start of the 10,000th frame whichcan be used to apply the code 56 to the command line 16 at the beginingof the two frames. The matter of controlling the sequencing and timingof the command signal is a matter well within the scope of one skilledin the art.

When the Hex number 56 appears on line 16 comparator 100 detectsequivalence between the first and second input and consequently producesan output which is applied to one input of OR gate 114. The OR gate 114produces an output which is applied to one input of AND gate 98 and alsoto the control input of a tristate buffer 116. Comparator 94 produces nooutput at this time and therefore the select input of multiplexer 92will be "low". When video clock data re applied on line 34 to themultiplexer 92 the multiplexer 92 will therefore select the video clockpulses and pass them through to the output of the multiplexer 92. Thesepulses are applied to the second input of AND gate 98 and, because thefirst input of the AND gate 98 is held high, the pulses are passedthrough and appear on line 52. Line 52 is connected to the read dataclock input of RAM 50 (FIG. 1).

Because comparator 94 has a low output at this time multiplexer 118selects the video input line 30 and passes it through to the tristate116 which, due to high state of the output OR gate 114, passes the videodata through to line 54. Line 54 is in turn connected to the WRITE datainput of RAM 50 (FIG. 1).

The output of AND gate 98 is also applied to the clock input of 16 bitcounter 120. Having been cleared initially by the Initialize pulse online 18, the counter 120 begins counting from 0 and applies the countoutput to the Low input of multiplexer 122.

The net result of the previously described sequence is that the videodata appearing on line 30 is clocked into the RAM at the clock ratedetermined by the video clock pulses on line 52 at a sequential seriesof address locations starting with 0000 which appear on line 56.

The receipt and storage of a block of Audio Coded Data is performed insubstantially the same manner by the control circuit 28 as thatdescribed for the receipt and storage of a block of Video Coded Data.However, in the case of the processing of Audio Coded Data, the outputof comparator 94 is "high" and therefore the Select inputs ofmultiplexer 92 and multiplexer 118 are "high". Thus, the Audio Clock online 48 and the Audio Coded Data on line 42 are passed through to lines52 and 54, respectively. Addresses are generated and applied on line 56in the same way.

A message unit is retrieved and read out in the following manner. Assumethat it is desired to play message unit 2 with a selected frame of videoin the stop motion mode. Using known techniques the player apparatus iscaused to play the selected video frame in the stop motion mode.Simultaneously, Hex 32, corresponding to the Play Message Unit Twocommand signal, is generated and applied to the command line 16. Thethree least significant bits of the command are applied to the SELECTinputs of both multiplexer 104 and multiplexer 106. The three leastsignificant bits of Hex 32 comprise the digital number "2" which, whenapplied to the SELECT input of multiplexer 104, selects the second inputconnected to switch 164. Switch 164, it will be recalled, is set to theaddress in RAM 50 of the second message unit pointer. This is applied tothe output of multiplexer 104 which is connected to the input of counter126.

Simultaneously, the four most significant bits of Hex 32 are applied tothe first input of comparator 102. Comparator 102 senses coincidencebetween that input and the outer of switch 112 which, it will berecalled, is set to the number 3. Coincidence causes the output ofcomparator 102 to go "high". This high signal is applied to the LOADinput of counter 126 which, in response loads the second message unitpointer value at the output of multiplexer 104 into the counter.

The high output of comparator 102 is also applying to the SELECT inputof multiplexer 122 which, in response, selects the HIGH input connectedto the output of counter 126. Thus, counter 126 which is at this timeset to the digital value corresponding to the second message unitpointer address in RAM 50 is applied through multiplexer 122 andmultiplexer 124 to line 56.

As the output of comparator 102 goes from a low value to a high value,one shot 128 is triggered. It will be noted that the Q outputs of oneshot 128 and one shot 156 are connected to the input of AND gate 54.Consequently, the normal state for the output of AND gate 154 is "high".When one shot 128 is triggered, it applies the negative going pulse toone input of AND gate 154, causing a negative going pulse to appear onthe output of AND gate 154. Because the output of divide-by-eight 144 isnormally "high", the negative going pulse appearing on the output andgate 154 is transmitted through AND gate 150 and appears on line 58. Theappearance on line 56 of the address of the second message unit pointerand the concurrent appearance of the negative going pulse on line 58cause the RAM 50 to provide on line 60 the contents of the RAM storagearea having the address of the first half of the second message unitpointer. The negative going pulse at the Q output of one shot 128 isalso applied to the LOAD input of register 152 which causes the eightbits retrived from the RAM 50 on line 60 to be stored in register 152.When the negative going pulse at the Q output of one shot 128 ends, ittriggers the rising edge input of one shot 156. This causes a negativegoing pulse having a duration of 500 nanoseconds to appear at the Qoutput of 156. This negative going pulse is applied to one input of ANDgate 154 which causes a negative going pulse to appear at the output ofAND gate 154 and, in turn, at the output of AND gate 150.Simultaneously, the negative going pulse at the Q output of one shot 156is applied to the CLOCK input of counter 126 which, in response,increments by one. This has the effect of increasing by one the pointernumber appearing on the address line 56. Consequently, the second eightbits of the second message unit pointer is retrieved from the RAM 50 andapplied to the line 60. Finally, the negative going pulse output at theQ output of one shot 156 is applied to LOAD input of register 160causing the second eight bits of the second message unit pointer to beloaded in register 160.

The net result of the sequence just described is that the entire secondmessage unit pointer is loaded in combination in register 152 and 160.The output of comparator 102 is low at this time and thereforemultiplexer 122 selects the LOW input and passes the count output ofcounter 120 through to the LOW input of multiplexer 124. Becauseflip-flop 136 is initially reset by the application of the Initializepluse from one shot 132 the SELECT input of multiplexer 124 is low and,consequently, the multiplexer 122 output is passed through to line 56.Line 56, it will be recalled, is connected to the RAM ADDRESS input ofRAM 50.

The twelve most significant bits of the second message unit startaddresses appearing at the output of registers 152 and 160 are appliedto the input of sixteen-bit counter 138. The 4 least significant bits ofthe output of registers 152 and 160 is applied to the SELECT input ofVariable Rate Clock Generator 142.

The counter 138 is thus prepared to be loaded with the start address,corresponding to the first 8-bits of the second message unit data. Thisaddress value is loaded into the counter 138 and applied to the RAM 50in the following manner. The negative going pulse at the Q output of oneshot 156 is applied to a one microsecond delay circuit 158 which delaysthe negative going pulse by one microsecond and then applies it to theSET input of flip-flop 136 and to the LOAD input of counter 138. Thus,in response to the negative going pulse at the Q output of one shot 156,counter 138 is loaded with the second message unit start address andthis address is applied to the HIGH input of multiplexer 124.Simultaneously, flip-flop 136 is set and its Q output is applied theSELECT input of multiplexer 124 causing it to select the HIGH input towhich the output of counter 138 is connected. This causes the startaddress to be applied to line 56.

The delayed output of delay 158 is also applied to the RESET input offlip-flop 134 causing the Q output of flip-flop 134 to go low, releasingthe Variable Rate Clock Generator 142. The four least significant bitsof the second message unit start address, which comprise the sample ratecode number, are present at this time at the SELECT input of the ClockGenerator 142 which, when released from hold, produces as an output aclock at the rate selected in accordance with the code at the input ofthe generator 142.

The clock from Clock Generator 142 is applied to the input of thedivided-by-eight device 144. Following eight counts of this clock anoutput appears at the output of divide-by-eight 144 which is applied toone input of AND gate 150. This causes a negative going pulse to appearon line 58 which causes the data at the start address storage locationin RAM 50 to appear at line 60.

This data on line 60 is applied to the input of parallel-to-serialconverter 146 and loaded immediately because of the presence of theoutput of divide-by-eight 144 at the LOAD input of 146. The loaded datais immediately clocked out serially in response to the clock pulsesappearing at the CLOCK input of the converter 146 from the output ofClock Generator 142. The serially clocked out data is applied to line62.

After four CLOCK pulses from Clock generator 142, the output ofdivide-by-eight 144 goes low. This causes the output of AND gate 150 togo low, thereby instructing the RAM 50 to read the data at the addresswhich is present on line 56. The data which is thus read is supplied online 60 and is thereby applied to the input of the parallel-to-serialconverter 146. During this time period, the clock output from ClockGenerator 142 is applied to one input of AND gate 148. However, theother input of AND gate 148 is held low by the Q output of flip-flop140, and consequently, the clock from Clock Generator 142 is inhibitedfrom appearing on line 66. The first 4 pulses from Clock Generator 142are also applied to the clock input of parallel-to-serial converter 146,and thus random data is clocked out on line 62. This output is notprocessed by the demodulator, however, since no clock pulses appear atthis time on line 64.

After four more clock pulses from clock Generator 142, the output ofdivide-by-eight 144 goes high. This triggers the CLOCK input of counter138, triggers the Load input of the parallel-to-serial converter 146,and triggers the input of one shot 174. One shot 174 is set to producean output pulse having a duration of 100 nanoseconds. Thus, as theoutput of divide-by-eight 144 goes high, the counter 138 is incrementedby one thereby causing the address appearing on line 56 to beincremented by one, data is loaded into the parallel-to-serial converter146, and one shot 174 is triggered thereby producing a negative-goingpulse which activates the set input of flip-flop 140. The Q output offlip-flop 140 thus goes high, enabling a string of clock pulses from theclock generator 142 to appear on line 64. Consequently, data isimmediately clocked out of the parallel-to-serial converter onto line62, and simultaneously clock pulses are provided on line 64.

Following four more clock pulses from Clock Generator 142, the output ofdivide-by-eight 144 again goes low. This causes another negative-goingpulse to appear on line 58 which causes the RAM 50 to access data fromthe storage location having the address location appearing on line 56which, it will be appreciated, is next storage location in the sequenceof the second message unit. After four more pulses at the output ofClock Generator 142, all of the data previously loaded in theparallel-to-serial converter 146 is completely clocked out onto line 52.Coincident with the output of divide-by-eight 144 going high, theparallel-to-serial converter 146 is loaded with the next eight bits ofdata which are present on line 60, counter 138 is incremented by one,and one shot 174 is triggered. Thus, the next eight bits of data areimmediately clocked out onto line 62 with no interuption from theclocking of the first eight bits of data. Flip-flop 140 already havingbeen set by the first positive-going edge appearing at the output ofdivide-by-eight 144, the Q output of flip-flop 140 remains high and thestream of clock pulses continues to appear on line 66 withoutinteruption.

The output of counter 138, in addition to being applied throughmultiplexer 124 to line 56 to provide the address information for theRAM 50, is also applied to one input of comparator 130. The other inputof comparator 130 is connected to the output of multiplexer 106.Multiplexer 106, it will be recalled, has at its output the thirdmessage unit pointer set in switch 170. Counter 138 continues toincrement with every cycle of the output divide-by-eight 144 therebyclocking, storage location by storage location, the entire contents ofthat portion of RAM 50 memory containing the data associated with themessage unit being accessed, in this example being the second messageunit.

When the output of counter 138 equals the subsequent message unitpointer, in this example message unit number 3, comparator 130 detectscoincidence and produces an output. This output is applied to the inputof one shot 132 which produces a one microsecond negative-going outputpulse on the Q output thereof. This negative going output pulse isappied to the SET input of flip-flop 134 which causes the Q output offlip-flop 134 to go high. This causes the HOLD input of Variable RateClock Generator 142 to go high which inhibits Clock Generator 142.Simultaneously, the negative-going output pulse from one shot 132 isapplied to the Initialize line, thereby clearing and resetting thevarious devices responsive to the Initialize pulse, returning thecircuit to its initial state awaiting a further command.

Thus, it has been shown that units of encoded audio data comprisingmessage units capable of being decoded at an associated particular clockrate for separate playback with selected video frames played in the stopmotion mode can, according the principles of the present invention, begrouped together along with specially encoded message unit pointers toform a block of encoded audio message data which may be recorded on arecording medium, such as a video disc, on either a portion of the discreserved for video information or on a portion of the disc reserved foraudio frequency information. This block of data can be recovered fromthe disc, stored in a storage device such as a RAM and selectivelyaccessed from the storage device and processed for controllable separateplayback of each message unit with a selected frame of video played inthe stop motion mode. In fact, the present invention provides sufficientflexibility over the control of the access and processing of the messageunits that the separate message units may be played back not only when asingle selected frame of video is played in a stop motion mode, but inaddition during any desired mode of video disc playback, for example,slow motion playback or skip frame playback.

It should be noted that while the control circuit 28 described aboveprovides an effective means for coordinating the storage and selectiveaccessing of data according to the principles of the present invention,it may be more cost effective to implement the logic contained incontrol circuit 28 in the program of a microprocessor, and have themicroprocessor exercise the function of the control circuit. Such animplementation is, in fact, considered preferred. The details of theprocedure for programming a microprocessor in this manner are notincluded herein, since such procedures are well known in the art and thederivation of an effective program for this function for a particularmicroprocessor is considered routine once the principles divulged hereinare known.

It will be appreciated from the foregoing that the present inventionrepresents a significant advance in the field of extraordinary modeaudio recording and playback, especially as applied to the field of stopmotion audio information recording and in playback. In particular, theinvention provides an effective technique for providing expandedflexibility in the efficient storage of encoded audio data in the formof separate audio data message units, and in the controllable selectionof the sampling rates of the data. It will also be appreciated thatalthough specific embodiments of invention have been described in detailfor purposes of illustration, modification may be made without departingfrom the spirit and scope of the invention. Accordingly, the inventionis not to be limited, except as by the appended claims.

What is claimed is:
 1. A method for playing back a selected one of aplurality of discrete audio mesage units included in a block ofcomposite digital audio data recorded on a record medium as a firstsequential series of said plurality of discrete audio message units, anda second sequential series of a corresponding plurality of messagepointer units, the entirety of said second sequential series occurringon the record medium upstream of the entirety of said first sequentialseries, said method comprising the steps of:employing a player means forrecovering said block of composites digital audio data from the recordmedium; storing said recovered block of composite digital audio datawithin an addressable digital data storage means operatively associatedwith said player means, with each of said message pointer units beingstored at respective, fixed storage locations within said storage means,and each of said audio message units being stored at respective,predetermined storage locations within said storage means; generating acoded message select command signal indentifying the selected one ofsaid plurality of audio message units; employing means operativelyassociated with said storage means and responsive to said coded messageselect command signal for retrieving said message pointer unitcorresponding to said selected audio message unit from its said fixedstorage location within said storage means, wherein each of said messagepointer units includes sampling rate code information indicative of apredetermined digital sampling rate at which its corresponding saidaudio message unit is to be decoded, said operatively associated meansbeing further responsive to said coded message select command signal forretrieving said selected audio message unit from its said predeterminedstorage location within said storage means; deriving said sampling ratecode information from said retrrieved message pointer unit correspondingto said selected audio message unit; employing means responsive to saidderived sampling rate code information for decoding the retrieved saidselected audio message unit at said predetermined digital sampling rateindicated by said derived sampling rate code information; and, employingsaid player means to play back the decoded said selected audio mesageunit.
 2. The method as set forth in claim 1, wherein said plurality ofdiscrete audio message units are discretely associated with a singleframe of video data also recorded on the record medium, and whereinfurther, said method further comprises the step of employing said playermeans to play back said single frame of video data associated with saidplurality of discrete audio message units, in a stop-motion mode ofoperation, in conjunction with said step of employing said player meansto play back the decoded said selected audio message unit.
 3. The methodas set forth in claim 1, wherein said fixed storage locations aresequentially addressed.
 4. The method as set forth in claim 1, whereinsaid predetermined storage locations are sequentially addressed.
 5. Themethod as set forth in claim 1, wherein said predetermined digitalsampling rate indicated by said message pointer units is variable. 6.The method as set forth in claim 1, wherein at least preselected ones ofsaid predetermined digital sampling rates indicated by said messagepointer units are different from each other.
 7. The method as set forthin claim 1, wherein the length of at least preselected successive onesof said audio message units differs.
 8. The method as set forth in claim1, wherein the length of said plurality of discrete audio message unitsis variable.